Fossil fuels or mineral fuels are
fossil source fuels, that is, hydrocarbons found within the top layer of the
It is generally accepted that they
formed from the fossilized remains of dead plants and animals by exposure to
heat and pressure in the Earth's crust over hundreds of millions of years. This
is known as the biogenic theory and was first introduced by Mikhail Lomonosov
Russian writer, chemist, and
astronomer, who made important contributions to both literature and science
Fossil fuels are non-renewable
resources because they take millions of years to form, and reserves are being
depleted much faster than new ones are being formed.
When coal, natural
gas or oil are burned, they release gases into the atmosphere:
(CO2) is a "greenhouse gas," trapping heat in the lowest part of
the earth's atmosphere. This contributes to "global warming" - the
average temperature of the earth slowly increases, affecting ecosystems
across the globe.
(SO2) is a key contributor to acid rain, primarily in the northeast U.S.
Nitrogen oxide (NOx)
contributes to acid rain and smog, as well as health issues such as lung
inflammation, immune system changes and eye irritation.
There are three major forms of
is an abundant fossil resource that consists mostly of carbon.
Energy content (Btu/pound) ranges from 5,000 to 15,000 depending on
the type of coal. Coal reserves are located all over the world.
Electric utilities consume about 87 percent of the total coal
produced. In the United States, coal is used to generate more than
half of all the electricity produced. It is also used as a basic
energy source in many industries, and as a heating fuel. The U.S. is
one of the top exporters of coal in the world. Most exported U.S.
coal goes to Western Europe, Canada, and Japan. Coal is recovered
from the earth by surface mining or deep mining. Surface mining, or
strip mining, is less expensive and usually occurs on flat land.
Deep mining requires digging shafts and tunnels to get to the coal
seam. Automation of deep mining has helped to counter its safety and
health hazards. Coal can be gasified to form a synthetic fuel
similar to natural gas. It can also be liquefied to make a synthetic
crude oil. To date, it has not been economical to make synthetic
fuels from coal on a large scale. As processes become more
efficient, the use of synthetic fuels may become more economical.
Oil comes from crude
oil, which is a mix of hydrocarbons with some oxygen, nitrogen, and
sulfur impurities. One barrel of oil (42 U.S. gallons) can provide
about 6 million Btu. Crude oil reserves are found all over the
world, but the Middle East alone has about 63 percent of the known
reserves. Of the oil consumed in the United States, most is used in
transportation, and much of the rest goes to industrial, commercial,
and residential uses. Crude oil is used to produce not only a range
of fuels, but also petrochemical ingredients for plastics, inks,
tires, pharmaceuticals, and a host of other products.
exploration technology and practices have led to the discovery of as
many new reserves as have already been used. To make the most of
this valuable resource, energy producers are developing more
efficient refining methods, product makers are finding more
efficient ways to use petrochemicals, and manufacturers are
developing more efficient cars. New techniques of locating and
extracting oil from the earth are also making it possible to recover
oil that was once too expensive to produce.
Oil is usually
recovered by drilling wells through the non-porous rock barrier that
traps the oil. In general, about 30 percent of the oil trapped can
be economically recovered by pumping. "Secondary" recovery
can remove another 10 percent, by flooding the well with
high-pressure water or gas. Another 10 percent can sometimes be
recovered with "tertiary" methods that heat the oil to
scrub it out. About half of the oil is left trapped in the rock. Oil
producers are continually seeking economical ways to recover more of
The oil refining
process separates crude oil into different hydrocarbons and removes
impurities such as sulfur, nitrogen, and heavy metals. The first
step is fractional distillation, a process that takes advantage of
the fact that different hydrocarbons boil at different temperatures.
In a tall tower called a fractionating column, crude oil is heated
until it boils. Horizontal trays divide the column at intervals. As
the oil boils, it vaporizes. Each hydrocarbon rises to a tray at a
temperature just below its own boiling point. There, it cools and
turns back into a liquid.
fractions are liquefied petroleum gases (propane and butane) and the
petrochemicals used to make plastics, fabrics, and a wide array of
consumer products. Next come gasoline, kerosene, and diesel fuel.
Heavier fractions make home heating oil and fuel for ships and
factories. Still heavier fractions are made into lubricants and
waxes. The remains include asphalt.
The refining process
then continues, with heavy fractions converted into lighter
fractions. In most cases, "cracking" processes are used to
transform large (heavy) hydrocarbon molecules and make the smaller,
lighter molecules such as gasoline and jet fuel. Better refining
technologies have made it possible to produce over 21 gallons of
gasoline from a 42-gallon barrel of crude oil-a remarkable advance
over the industry's early days, when a barrel of oil yielded just
11 gallons of gasoline.
Oil shale was never
buried deeply enough or heated enough to form crude oil. Its
hydrogen content is between that of coal and crude oil.
Concentrations of oil are low, so that, at most, one barrel of oil
can be recovered from 2.4 tons of sand or 1.5 tons of rock. Huge
amounts of oil shale are found all over the world. In fact, the
total global resource is 1,000 times greater than crude oil
reserves. But extracting the energy value of oil shale is not
practical today. Scientists and engineers continue working on ways
to recover oil shale for a reasonable cost.
Natural gas is the
gas component of coal and oil formation. It is used in industrial
and commercial heating and cooking, and, increasingly, to fuel
electricity generation. In a compressed form, natural gas can also
be used as a transportation fuel. Natural gas is either found mixed
in oil or is released from coal. Energy in 6,000 cubic feet of
natural gas is equivalent to one barrel of oil. World reserves of
natural gas are greatest in Russian, Iran, Qatar, Saudi Arabia,
United Arab Emirates, and the U.S. The U.S. consumed 19.7 million
cubic feet of natural gas in 1999, nearly all of which came from
domestic production. Five states-Texas, Louisiana, Alaska, New
Mexico, and Oklahoma-hold more than 85 percent of U.S. natural gas
Wells for natural gas
are drilled in underground reservoirs of porous rock. When it is
removed from a reservoir, natural gas can either be pumped to the
processing station for removal of liquid hydrocarbons, sulfur,
carbon dioxide, and other components, or stored in large caverns
underground until it is needed. Pipelines are the main method of
transporting natural gas. Natural gas can also be liquefied and
shipped overseas, but this process is complex and expensive.
by natural gas has been improved by the development of
combined-cycle systems. These systems put together a
natural-gas-fueled combustion turbine with a heat-recovery steam
generator and steam turbine, to produce electricity in two ways
rather than just one. The result: roughly 60 percent of the heat
from the natural gas is harnessed to make electricity, creating a
more energy-efficient system.
All three were formed many
hundreds of millions of years ago before the time of the dinosaurs - hence the
name fossil fuels. The age they were formed is called the Carboniferous Period.
It was part of the Paleozoic Era. "Carboniferous" gets its name from
carbon, the basic element in coal and other fossil fuels. The Carboniferous
Period occurred from about 360 to 286 million years ago. At the time, the land
was covered with swamps filled with huge trees, ferns and other large leafy
plants. The water and seas were filled with algae
- the green stuff that forms on a stagnant pool of water. Algae is actually
millions of very small plants.
All fossil fuels, whether solid,
liquid, or gas, are the result of organic material being covered by successive
layers of sediment over the course of millions of years. Some deposits of coal
can be found during the time of the dinosaurs. For example, thin carbon layers
can be found during the late Cretaceous Period (65 million years ago) - the
time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the
Carboniferous Period. Fossil fuels supply over 80% of the world's
Coal is derived from the accumulation
of partially decayed land plants. As the sediment solidifies into rock, the
organic material decomposes under the influence of great pressure and high
United States uses about 20.8 million barrels of oil every day.
Fuels account for nearly 80% of our country's energy.
Coal is used to produce almost
60% of our nations electrical power, and accounts for 22% of our overall
Natural gas, a third form of
fossil fuel, accounts for roughly 23% of The United States energy usage.
It takes the equivalent of 7
gallons of gasoline per day for every man woman and child to keep this
country running at its current pace.
The U.S. is home to 4% of the
world's population, yet consumes 26% of the world's energy.
The earliest known use of coal
was in China. Coal from the Fu-shun mine in northeastern China may have been
used to smelt copper as early as 3,000 years ago
Oil has been used for more
than 5,000-6,000 years. The ancient Sumerians, Assyrians and Babylonians
used crude oil and asphalt ("pitch") collected from large seeps at
Tuttul (modern-day Hit) on the Euphrates River. A seep is a place on the
ground where the oil leaks up from below ground. The ancient Egyptians, used
liquid oil as a medicine for wounds, and oil has been used in lamps to
Sometime between 6,000 to
2,000 years BCE (Before the Common Era), the first discoveries of natural
gas seeps were made in Iran. Many early writers described the natural
petroleum seeps in the Middle East, especially in the Baku region of what is
now Azerbaijan. The gas seeps, probably first ignited by lightning, provided
the fuel for the "eternal fires" of the fire-worshiping religion
of the ancient Persians.
Fossil fuels - coal, oil and
natural gas -- currently provide more than 85% of all the energy consumed in
the United States, nearly two-thirds of our electricity, and virtually all
of our transportation fuels. Moreover, it is likely that the
nation's reliance on fossil fuels to power an expanding economy will
actually increase over at least the next two decades even with aggressive
development and deployment of new renewable and nuclear technologies.